Abstract: Biyang fault-depression experienced three evolutional phases: pull-apart during Mesozoic, rift during Paleogene, and downwarping in Neogene. Accordingly, three basin-fill sequences and corresponding tectonic sequences have developed. These sequences are defined by regional unconformities, with their general sedimentary style being respectively assemblage of fluvial fan-flood-lake depositional systems, fluvial fan-fan delta-lacustrine-delta depositional systems, and fluvial plain-sand-mud flat-coastal-shallow lacustrine depositional systems. Tectonic sequence II ( Eogene) comprises the main sedimentary fill of the basin and can be divided into seven seismic sequences, each of which exhibits specific depositional system configuration. The Hetaoyuan Formation (Eh), a major target of petroleum exploration in the basin, can be further divided into twelve sequences, whose boundaries are mainly discontinuous or transformed facies interfaces, or in minor cases are subaerial erosion surfaces or depositional hiatus.

Key words: Biyang fault-depression, Continental facies, Sedimentary sequence, Sedimentary type, Sedimentary facies